1. Field of the Invention
The invention relates to a hydraulic catapult drive in accordance with the preamble of claim 1.
2. Description of the Related Art
Hydraulic catapult drives of this type are used for accelerating an object, for instance an aircraft along a launching pad or a passenger train of a roller coaster or the like. In WO 01/66210 A1 a catapult drive is shown by which a car of a fairground ride can be accelerated along an acceleration track. The catapult drive comprises a driving car driven by a hydraulic motor and a flexible drive on which the car to be accelerated is supported. The hydraulic motor drives a winch which is wrapped in opposite sense by two pull ropes both of which act upon the car. Upon acceleration one of the pull means is wound on the winch, while the other pull rope correspondingly unwinds. When resetting the car into its home position the direction of rotation of the hydraulic motor is reversed so that the former pull rope is wound and the latter pull rope is unwound. The flexible drive is tensioned via a tensioning rope of a further flexible drive during acceleration and resetting.
U.S. Pat. No. 6,837,166 B1 discloses a catapult drive for a fairground ride in which the driving element is accelerated via a flexible drive and a hydraulic cylinder by which a movable set of pulleys of the flexible drive is axially movable. In this catapult drive, at the driving element a pull rope of a further flexible drive is additionally fixed the end portions of which similar to the afore-described embodiment—can be wound onto a winch or unwound from the same so that the driving element is reset to the home position by appropriately driving the winch, wherein then also the hydraulic cylinder is returned to its home position by the movable set of pulleys.
In WO 2004/024562 A1 a catapult drive is disclosed in which the acceleration of the driving element takes place via a flexible drive and a hydraulic cylinder in the form of a differential cylinder the bottom-side cylinder chamber of which can be pressurized by the pressure in a high-pressure reservoir when extending the piston rod. The piston rod of the differential cylinder supports two movable sets of pulleys which are wrapped by a common pull rope to which the driving element is fixed. The hydraulic cylinder is reset to its home position via a separate resetting cylinder which is likewise in the form of a differential cylinder and the piston rod of which returns that of the differential cylinder used for acceleration against the force applied by the hydraulic reservoir to its home position.
The above-described catapult drives require a comparatively high expenditure in terms of devices, because for acceleration and resetting of the driving element different actuating members are used which have to be controlled in an appropriate manner.